A flange adapter is a multi-piece assembly that, when assembled, joins a grooved pipe to a flanged pipe. The assembled flange adapter has a grooved-pipe end with an inner diameter surface that fits over an end of the grooved pipe. The grooved-pipe end also has a tongue extending inwardly from the inner diameter surface that engages a groove on the outer surface of the grooved pipe. The grooved-pipe end of the flange adapter is typically secured to the grooved pipe by placing the tongue within the groove, and by assembling the multi-piece structure of the flange adapter together so that the groove retains the flange adapter on the end of the grooved pipe. The flange-end of the flange adapter has an adapter flange that engages a pipe flange on the flanged pipe. The pipe flange is typically secured to the adapter flange with bolts inserted through common bolt holes that pass through the flange adapter and the pipe flange. The inner diameter surface of the flange adapter also typically holds a gasket disposed between the facing ends of the grooved and flanged pipes to provide a seal between the pipes.
Existing flange adapter assemblies are believed to have several disadvantages. Existing flange adapters for pipes with diameters greater than 12 inches are believed to be made of four quarter-round components that must be joined together to form the flange assembly. Such four-piece flange assemblies require at lease four points of connection to connect each quarter-round component to adjacent components, which requires at least four connecting bolts and additional time to assemble as compared to a two-piece flange assembly. At each point of connection, each quarter-round component must also have additional material or reinforcement structures to provide support for connecting bolts joining one quarter-round to another quarter-round, which undesirably adds weight to the assembled four-piece flange assembly.
Some existing flange adapter systems are designed so that the common bolt holes connecting the adapter flange and pipe flange pass through two mating pieces of the flange adapter assembly, as described, for example, in U.S. Pat. Nos. 6,264,251, 6,315,335, and 7111876. In such an arrangement, the ends of each flange piece have areas-surrounding certain bolt holes that are about half the thickness of the remainder of the flange piece. When these half-thickness portions are aligned with an adjacent flange piece, the two portions together form an area having a thickness similar to the remainder of the flange piece and a single common bolt hole shared between the adjacent flange pieces. A disadvantage with such an arrangement is that the half-thickness portions of each flange piece are structurally weaker than areas of the flange pieces having a full thickness, and the change in flange piece thickness complicates the casting of the flange piece. Also, during assembly of two adjacent flange pieces, additional skill and time are required because the assembly requires the alignment of a common bolt and two or three components forming the common bolt hole, e.g., the simultaneous alignment of the common bolt, the alignment of the common bolt holes passing through the two mating half-thickness portions of the flange piece, and the alignment of the bolt hole passing through the pipe flange. In larger flange pieces having a greater weight, the manipulation and alignment of multiple components can be hazardous. Another disadvantage is realized when the flange adapter assembly includes both common bolt holes and circumferentially-aligned bolts joining one flange piece to another, as described in the Gruvlok Data Sheet 5 (2004) and the Vic-Flange Adapters product specification for Styles 741 and 743 (Rev. G, 10/2006), for example. When the circumferentially-align bolts are tightened, the movement of one flange piece towards the adjacent flange piece can subject the common bolt passing through the two half-thickness portions to undesirable shear forces.
Other existing flange adapter assemblies provide mating surfaces between adjacent flange pieces that are not planar, with a projection of one flange piece mating surface being inserted into a cavity in the mating surface of an adjacent flange piece. Such designs may prove to be problematic during assembly because the cavity is prone to capturing dirt and debris that could interfere with the proper seating of the projection within the cavity. Also, the available area of the mating surface is reduced by the positioning of the cavity within the mating surface. In such arrangements, the endmost portion of the projection may not contact the bottom of the cavity because the projection is designed to be shorter than the depth of the cavity so as to not bottom out. Since a portion of the mating surface is dedicated to the projection and cavity, which do not fully contact each other, the amount of contact between adjacent mating surfaces is undesirably reduced.
Yet other existing flange adapter designs have mating surfaces that come together near the gasket. It is believed that the pieces of a multi-piece flange adapter are loosely assembled in place on the grooved pipe, the gasket is inserted, the adapter flange is connected to the pipe flange, and the bolts connecting the adapter pieces are tightened. During this tightening, it is possible that the gasket could be pinched between the mating surfaces of adjacent flange pieces as those surfaces come together. An example of mating surfaces coming together near a gasket is described in the Victaulic I-100 Field Installation Handbook, pp. 113-118.
Thus, what is needed is a flange adapter that overcomes the disadvantages of existing designs by providing a two-piece flange adapter for pipe having diameters greater than 12 inches, while avoiding the use of shared bolt holes between flange pieces, providing an uninterrupted mating surface, and preventing the pinching of the gasket by adjacent flange pieces.